The present invention relates to an image sensor for use in an image input portion of a facsimile machine, a copying machine, or the like.
FIGS. 9, 10, 11A and 11B are views showing a related-art image sensor. FIG. 10 is a top view of the related-art image sensor. FIG. 9 is a sectional view taken on line B–B′ in the image sensor of FIG. 10. FIG. 11A is a perspective view of a sensor frame for the image sensor after the sensor frame has been extrusion-molded of metal or resin but not yet subjected to machining. FIG. 11B is a sectional view of the sensor frame at a longitudinally central portion. In FIG. 9, the image sensor includes: a manuscript 10; a line light source 20 such as a lamp or a linear array of LED chips that can illuminate the manuscript 10 linearly; a rod lens array 30 constituted by a plurality of rod lenses (not shown) for forming a correct life-size image; a sensor substrate 40; a linear array of sensor ICs 50 formed on the sensor substrate 40; a transparent plate 60 located on a manuscript running plane; and a sensor frame 70 formed by extrusion-molding of metal or resin. The sensor frame 70 is constituted by frames 70a and 70b located on opposite sides of the rod lens array 30. In the sensor frame 70, there is further provided: a light passageway 71 which is disposed under the rod lens array 30 and through which light reflected by the manuscript passes before the reflected light enters the sensor ICs 50; a support portion 72 for supporting the frames 70a and 70b with each other; a lens array holding portion 73 for holding the rod lens array 30; machined surfaces 74 cut by machining with a result that foreign matter such as burrs and flash is produced on the machined surfaces; and sensor substrate mount portions 77 for mounting the sensor substrate 40. The image sensor further includes: a light course 80 through which light emitted from the line light source 20 is formed into an image on the sensor ICs 50; and fixing members 90 such as screws for fixing the sensor substrate 40 onto the sensor frame 70.
In FIG. 10, there are further provided plates 100 attached to the opposite ends of the sensor frame 70 so as to close a space where the light source 20 is disposed and another space where the sensor ICs 50 are located. The longitudinal direction and the transverse direction are defined by the arrows illustrated in the drawings. In addition, in FIGS. 11A and 11B, a material 75 is an extruded material of the sensor frame manufactured by extrusion but not yet subjected to machining.
Next, description will be made on the operation. The light from the line light source 20 is transmitted through the glass plate 60 and illuminates the manuscript 10 uniformly. The illumination light is reflected, as shown in the light course 80, by the manuscript 10 in accordance with gray scale information of an image formed on the basis of the manuscript 10. Thus, the reflected light passing through the rod lenses of the rod lens array 30 and through the light passageway 71 is formed into an image on light-receiving portions of the sensor ICs 50. The sensor ICs 50 accumulate charges in accordance with the intensity of the reflected light, and output the charges through the sensor substrate 40.
FIGS. 11A and 11B are a perspective view and a sectional view of the sensor frame before machining. As illustrated in FIGS. 11A and 11B, the light formed into an image by the rod lens array 30 cannot be transmitted if the sensor frame before machining is left as it is. It is therefore necessary to form the light passageway 71 by cutting out the support portion 72 by machining while leaving the opposite ends of the support portion 72 as shown by the arrow C in FIG. 11B.
At that time, when the light passageway 71 is provided by machining, foreign matter such as burrs and flash is produced on the machined surfaces 74. A work for removing the burrs and flash from the machined surfaces 74 is therefore carried out. However, since the light passageway 71 is narrow, and the machined surfaces 74 are formed to be opened not to face the upper or lower surface of the sensor frame 70 but to face side surfaces thereof, it is impossible to remove the burrs and flash from the machined surfaces 74 perfectly. Thus, the image sensor is assembled with the sensor frame 70 while the foreign matter such as burrs and flash remains on the machined surfaces 74. However, the foreign matter such as burrs and flash may fall down from the lower portion of the light passageway 71 due to vibration or impact in transit after the shipment of the image sensor. Such foreign matter may remain in the space for the sensor ICs 50 and cover the light-receiving portions wholly or partially due to subsequent vibration or impact. Thus, there has been a problem that the gray scale information of an image formed on the basis of the manuscript 10 cannot be transmitted to the sensor ICs 50 correctly.
The Unexamined Japanese Patent Application Publication No. Hei7-162587 discloses an example in which the light passageway 71 is not provided by machining. FIGS. 12 and 13 show a related-art image sensor disclosed in the Unexamined Japanese Patent Application Publication No. Hei7-162587. FIG. 12 is a sectional view, and FIG. 13 is a view showing a section of an extruded material of a frame for the image sensor. A manuscript 10, a line light source 20, a rod lens array 30, a sensor substrate 40, sensor ICs 50, a transparent plate 60, a sensor frame 70, a light passageway 71, a support portion 72 and a light course 80 have the same configurations and the same operations as those shown in FIG. 9, respectively.
In this case, the transparent plate 60 and the sensor frame 70 are formed integrally with each other by extrusion molding of transparent plastic and colored metal or resin. Therefore, the light passageway 71 is provided over the whole length of the sensor frame 70 in advance, so that it is not necessary to provide the light passageway 71 by machining. In addition, the support portion 72 for supporting frames 70a and 70b with each other is located on the lower side of the sensor substrate 40. Thus, when the sensor substrate 40 is mounted on the support portion 72, the sensor substrate 40 is inserted into the sensor frame 70 from an end portion.
However, according to this method, the sensor substrate 40 is inserted into the sensor frame 70 and then assembled with the latter. The sensor substrate 40 and the sensor frame 70 may be rubbed against each other. Either the sensor substrate 40 or the sensor frame 70 may be shaved by this rubbing. The light-receiving portions of the sensor ICs 50 are wholly or partially covered likewise with such shaved material as foreign matter. Thus, there has been a problem that the gray scale information of an image formed on the basis of the manuscript 10 cannot be transmitted to the sensor ICs 50 correctly.